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Aquatic ape
The aquatic ape hypothesis (AAH), also referred to as aquatic ape theory (AAT) and more recently the waterside model, is the idea that certain ancestors of s were habitual waders, swimmers and divers. The hypothesis in its present form was proposed by the in 1960, who argued that a branch of apes was forced by competition over terrestrial habitats to hunt for food such as on the sea shore and sea bed leading to s that explained distinctive characteristics of modern humans such as functional hairlessness and . This proposal was built upon by in her 1972 book The Descent of Woman. History The German (1871–1957) discussed in 1942 various human characteristics ( , , the regression of the , , direction of the etc.) that could have derived from an aquatic past, quoting several other authors who had made similar speculations. He stated: "The postulation of an aquatic mode of life during an early stage of human evolution is a tenable hypothesis, for which further inquiry may produce additional supporting evidence." The Hardy/Morgan hypothesis Independently of Westenhöfer's writings, the had since 1930 also hypothesized that humans may have had ancestors more aquatic than previously imagined. On the advice of his colleagues, Hardy delayed presenting the hypothesis for approximately thirty years. After he had become a respected academic and knighted for contributions to marine biology, Hardy voiced his thoughts in an article in on 17 March 1960. Hardy's hypothesis as outlined in the was: :My thesis is that a branch of this primitive -stock was forced by competition from life in the trees to feed on the sea-shores and to hunt for food, , etc., in the shallow waters off the coast. I suppose that they were forced into the water just as we have seen happen in so many other groups of terrestrial animals. I am imagining this happening in the warmer parts of the world, in the tropical seas where Man could stand being in the water for relatively long periods, that is, several hours at a stretch. Hardy argued a number of features of modern humans are characteristic of aquatic adaptations. He pointed to human's lack of body hair as being analogous to the same lack seen in certain other marine mammals, such as the and the , and noted the layer of humans have that Hardy believed other apes lacked, although it has been shown that captive apes with ample access to food have levels of subcutaneous fat similar to humans. Additional features cited by Hardy include the location of the in the rather than the nasal cavity, the human propensity for front-facing , and , though these claimed pieces of evidence have alternative evolutionary adaptationist explanations that do not invoke an aquatic context. Hardy additionally posited that evolved first as an aid to before becoming the usual means of human locomotion, and tool use evolved out of the use of rocks to crack open . These last arguments were cited by later proponents of AAH as an inspiration for their . Wading and bipedalism AAH proponent Algis Kuliukas, performed experiments to measure the comparative energy used when lacking with using fully upright posture. Although it is harder to walk upright with bent knees on land, this difference gradually diminishes as the depth of water increases and is still practical in thigh-high water. Diving behavior and performance Aside from working as a professor, Erika Schagatay is also an experienced and whose research centers around human diving abilities. She suggests that such abilities are consistent with selective pressure for underwater foraging during human evolution, and discussed other anatomical traits speculated as diving adaptations by Hardy/Morgan. John Langdon suggested that such traits could be enabled by a human . Vernix caseosa Tom Brenna, professor of pediatrics whose primary research focuses on fats, oils, and fatty acids, listened to the 2005 radio documentary Scars of Evolution where David Attenborough reported an observation that s were born with something that resembled human . Intrigued, Brenna led a team that collaborated with Judy St Leger at to compare the chemistry of human vernix and samples from pups. They established that the molecular composition of both is similar, being rich in and . References Category:Life